Anisotropic compounds and liquid crystal mixtures

ABSTRACT

New anisotropic compounds with a cross-polarizing substituent have the formula (1) ##STR1## The increase in ε⊥ is achieved by the polarizing group X, preferably the cyano group or a halogen atom, which is not laterally on the ring, as with the known compounds, but is on the bridge, that is to say is part of the main bridge bonding rings A and B to one another. Ring A has the formula (1a) or (1b) given herein and is always cycloaliphatic, while ring B can be identical to ring A or is an aromatic ring of the formula (1c) or (1d) herein. R 1  and R 2  are identical or different end groups of the formula (1e) herein. 
     The radical X on the bridge causes less widening of the molecule than a radical X on a ring, which provides comparatively higher clear points and moreover enables aromatic rings to be omitted from the anisotropic compounds.

This application is a continuation-in-part of U.S. application Ser. No.648,439, filed Sept. 10, 1984, now U.S. Pat. No. 4,622,163.

BACKGROUND OF THE INVENTION

The invention relates to new anisotropic compounds which carry at leastone cross-polarizing substituent and offer reduced viscosities andincreased clear points; the invention furthermore relates to liquidcrystal mixtures (LC mixtures) containing these compounds as components.

As is known, nematic LC mixtures with negative Δε values are requiredfor various types of electrooptical displays, for example for theso-called "guest/host displays" (GHD) and the homeotropic-nematicdisplays (HND), Δε being designated DC anisotropy or DCA and beingdefined as Δε=ε"-ε⊥', wherein ε" is the dielectric constant (DC)parallel to the longitudinal axis of the molecule and ε⊥ is the DCperpendicular to the molecular axis.

Furthermore, for certain types of operation of the displays, for examplefor multiplex operation, LC mixtures with an overall positive DCA but assmall as possible a value of the ratio ##EQU1## are required, that is tosay mixtures or compounds with a significant value for ε⊥.

The values of ε" and ε⊥ are determined by the degree of polarization ofthe molecule in the direction parallel and, respectively, perpendicularto the longitudinal axis of the molecule; for example, a highlypolarizing substituent, such as the cyano group or a halogen atom, as anend group--also designated a longitudinally polarizing substituentbelow--increases the value of ε", while such a substituent in the"lateral" position, that is to say more or less at right angles to thelongitudinal direction of the molecule, increases the value of ε⊥; theselateral substituents are here designated "cross-polarizing"substituents.

However, the LC mixtures and their components must also fulfil a numberof other characteristics, including, in particular, a highphotochemical, general chemical, heat and electrochemical stability andas low as possible a viscosity and low optical anisotropy (low tendencytowards double refraction) and clear points which are as high aspossible.

According to the prior art, negative DCA values or higher ε⊥contributions are generally achieved by providing an aromatic cyclicradical, usually a benzene ring, with at least one cross-polarizingsubstituent.

The known compounds with negative DCA thus have, as the characteristicelement, cores having the structure ##STR2## in which X' is thecross-polarizing group, for example cyano or halogen, n is 1 or 2 andthe arrows approximately correspond to the longitudinal axis of themolecule. Such compounds are described, for example, in German Pat. Nos.A-2,240,864, 2,613,293, 2,835,662, 2,836,086, 2,835,728 and 2,937,770and European Pat. No. A-0,023,728.

It is furthermore known, from European Patent Application No.79,200,259.4, that at least one cross-polarizing substituent can becombined with a longitudinally polarizing substituent to obtainanisotropic compounds with positive DCA and small values of the ratio##EQU2##

The known compounds have the common factor of widening of the moleculeas a result of the cross-polarizing substituent or substituents, thisbeing a disadvantage because it leads to a reduction in the clear pointand frequently gives rise to a relatively high viscosity; since thelateral polarizing groups can in practice be introduced only intoaromatic radicals, the necessity of the presence of an aromatic radicalrepresents a further limitation.

SUMMARY OF THE INVENTION

Thus, it is an object of this invention to provide new anisotropiccompounds which carry at least one cross-polarizing substituent butcontain no cross-polarizing groups attached to cyclic radicals, so thatthe above disadvantages and limitations can be avoided.

Upon further study of the specification and appended claims, furtherobjects and advantages of this invention will become apparent to thoseskilled in the art.

According to the invention, these objects have been achieved byproviding new anisotropic compounds of the formula (1) which possess atleast two cyclic radicals bonded to one another via a particular bridgemember carrying the polarizing group (also designated the main bridgebelow): ##STR3##

DETAILED DISCUSSION

The ring A is a cycloaliphatic ring of the formula (1a) or (1b) ##STR4##that is to say a trans-1,4-cyclohexyl radical or a1,4-bicylco-(2,2,2)-octyl radical.

The ring B can also be a cycloaliphatic ring of the formula (1a) or(1b), or can be an aromatic radical of the formula (1c) or (1d) ##STR5##that is to say a 1,4-phenyl radical or a 3,6-pyridazinyl radical.

The polarizing group X, which is a halogen atom or the cyano group, mustbe attached to that C atom of the main bridge to which thecycloaliphatic radical, or one cycloaliphatic radical, is bondeddirectly. Since ring A must always be cycloaliphatic, while ring B canbe cycloaliphatic or aromatic, this results in the position of X shownin formula (1). If ring B is also a cycloaliphatic radical, X could alsobe attached to the C atom of the main bridge bonded directly to ring B.

The groups R¹ and R² in formula (1) are identical or different endgroups of the formula (1e) ##STR6## in which the ring C has one of themeanings given for ring B, that is to say is a radical of the formula(1a), (1b), (1c) or (1d), and thus can also be cycloaliphatic oraromatic; however, ring C in formula (1e) is optional, that is to say mis 0 or 1.

The bridge Z in formula (1e) is the covalent bond or a secondary bridgegroup of the formula --CH₂ O--, --C(X¹)(H)--CH₂ -- or --COO--, whereinX¹ is hydrogen or has one of the meanings given for X, and in particularin each case also in reverse sequence, the provisos (a) and (b)described below, however, also being taken into consideration.

If X¹ in the secondary bridge has one of the meanings given for X,additional lateral polarization can be effected. For many purposes, Z ispreferably in the form of a covalent bond.

R³ can be hydrogen, if m is 1 and ring C is a cyclic radical of theformula (1c) or (1d), or, generally, is alkyl (H_(2n+1) C_(n) --),alkoxy (H_(2n+1) C_(n) --O--), alkoxycarbonyl (H_(2n+1) C_(n) --OC(O)--)or alkylcarbonyloxy groups (H_(2n+1) C_(n) --C(O)--O--), the alkyl partof which contains 1-12 C atoms (n=1-12) in a straight or branched,optionally chiral chain. Examples of the alkyl parts of the groupsmentioned are thus methyl, ethyl, propyl, butyl, pentyl, hexy, heptyl,octyl, nonyl, decyl, undecyl and dodecyl groups, including the isomericand chiral-isomeric alkyl groups, such as 2-methylbutyl, 2-methylbutoxy,2-methylpentyl, 3-methylheptyl and the like. These alkyl partspreferably have a straight chain and 3-7 C atoms.

The alkyl parts of R³ can carry one or more substituents, in particularhalogen atoms or cyano groups, in each case at most one such substituentbeing attached to in each case one C atom of the alkyl part. The alkylparts of R³ preferably contain one or at most two such substituents, andin particular preferably on those C atoms of the alkyl part which arenot too far removed from the associated ring, for example which areattached to atoms in the 1-, 2- or 3-position of the end group chain, ifthe atom (C or O) bonded to the associated ring is designated the atomin the 1-position of the chain. Under certain circumstances, especiallyif the substituent is cyano, the contribution to the longitudinal orcross-polarization can be increased by attaching the substituent to aneven-numbered or odd-numbered atom of the chain of the end group.

Furthermore, fluorine, chlorine or cyano is in most cases preferred asthe substituent of the alkyl part of R³.

The actual conformation of the main bridge of the formula (1)corresponds to the equation ##STR7## and shows that the widening of themolecule caused by the laterally polarizing radical X on the bridge islower in the anisotropic compounds according to the invention than inthe known anisotropic compounds with X on the ring.

Concrete comparison values for the surprising improvements in theproperties of compounds (1) according to the invention with laterallypolarizing groups on the bridge as against comparable (in respect ofDCA) compounds with laterally polarizing groups on the ring are givenbelow in Example 2.

It is furthermore surprising that compounds with the stability requiredfor LC mixtures are obtainable at all with highly polarizing groups onthe bridge. Known compounds with cyano groups on the bridge have almostalways proved to be unstable, and investigations by the ApplicantCompany have shown, that, for example, compounds with the "cyanobenzylstructure" ##STR8## in which D is an aromatic ring, like compounds withthe "benzyl ether structure" ##STR9## here do not give compounds with anadequate stability.

The following provisos or restrictions thus apply to compounds of theformula (1) according to the invention:

(a) groups of the formulae ##STR10## are not bonded directly via their Catoms to any aromatic radical of the formula (1c) or (1d), except forwhen X=F, and

(b) R³ in formula (1e) is not hydrogen if m is 0.

Preferred groups of compounds of the formula (1) according to theinvention have the following features, individually or in combination:

X is the cyano group;

if X is halogen, fluorine and chlorine are preferred;

if R³ contains a substituted alkyl part, this preferably carries one ortwo substituents, preferred halogen atoms being fluorine and chlorine;

the molecule of the formula (1) preferably contains not more than onecarboxyl group in total;

the molecule of the formula (1) preferably contains not more than onearomatic ring of the formula (1c) or (1d);

the molecule of the formula (1) preferably contains not more than threecyclic radicals in total;

the molecule of the formula (1) contains two or three cycloaliphaticradicals of the formula (1a) and/or (1b);

the molcule of the formula (1) contains two end groups with alkyl parts,each of which has 3-9 C atoms;

the substituent or substituents (at most two) of the alkyl parts of R³are attached to those C atoms of the alkyl chain which are separatedfrom the associated ring, that is to say the next ring, by not more than2 atoms.

Compounds of the following formulae 2-5 are also preferred for manyintended uses: ##STR11## in which A, B, C, X, Z, R¹, R² and R³ have theabovementioned meaning, R⁴ and R⁵ have one of the meanings given for R³,and n is 0 or 1, with the exception of hydrogen; however, the inventionis not limited to binuclear or trinuclear compounds (1), since both R¹and R² can be identical or different groups of the formula (1e).Preferably, the compound of formula (5) has R³ and R⁴ groups both ofwhich are C₁₋₁₂ -alkyl groups, e.g., n-pentyl. Preferably, the compoundof formula (6) has a C₁ -C₁₂ -alkyl radical as R¹ group and ##STR12## asR² group.

The invention furthermore relates to liquid crystal mixtures whichcontain at least one compound of the formula (1), for example in amountsof 1-30% by weight, it also being possible for the mixture to containseveral different compounds of the formula (1), for example in a totalamount of 5-70% by weight, preferably 15-65% by weight. As furthercomponents, the LC mixtures according to the invention can contain knownanisotropic compounds and the additives appropriate for the intendeduse, such as dyestuffs, in particular pleochroic dyestuffs, opticallyactive or cholesteric components and the like. The preparation,compositions and use of the mixtures and electro-optical cells of thisinvention are fully conventional as described, e.g., in U.S. Pat. Nos.3,995,941; 3,951,846 and 4,285,829.

The new compounds of the formula (1) can be obtained by variousprocesses which are known per se; the compounds (1) in which X in themain bridge is the cyano group can be obtained, for example, directly bycondensation according to the following equation I:

Equation I ##STR13## wherein R¹, R², A and B have the abovementionedmeaning and L¹ and L² are leaving groups, such as, for example, L¹ =H,L² =Br and the like. The condensation reaction is preferably carried outhere in a liquid medium at elevated temperature in the presence ofsubstances which accelerates the condensation, such as, for example,metallic sodium, or which bond the compound L¹ L² formed as theby-product.

Suitable starting compounds of the formulae (11) and (12) are eitherknown or are obtainable in accordance with the following equation II:

Equation II ##STR14##

Suitable starting compounds (21) for the synthesis according to equationII are known, or they can be obtained in a similar manner to the knowncompounds.

The reduction can be carried out in a manner which is known per se, forexample with lithium aluminum hydride; the bromination is usuallyadvantageously carried out with elemental bromine in the presence oftriphenylphosphine, and the reaction with KCN can be achieved asdescribed in Org. Synth. Coll. volume 3, 852 (1955).

The starting compounds (12) corresponding to the compounds (23)##STR15## can also be obtained in an analogous manner according toequation II for the synthesis according to equation I, where B is anaromatic radical of the formula (1c) or (1d) and R¹ =R², by using thecorresponding carboxylic acids of the formula (210) ##STR16## in whichthe ring D is a radical of the formula (1c) or (1d), instead of thecompounds (21).

The following compounds are general examples of suitable compounds ofthe formulae (21) and (210): ##STR17## in which R¹ and R³ have theabovementioned meaning. The preparation of acids of the formula (21/4)is described, for example, in Mol. Cryst. Liqu. Cryst. 75 (1981) 95. Theacids of the formula (210/2) can be obtained from the chloro- orbromo-pyridazine derivatives described in Z. fur Chemie, 17 (1977) 333,using CO₂ /Mg (Grignard).

The compounds of the formula (1) in which X in the main bridge ishalogen can be obtained in accordance with the following equation III:

Equation III ##STR18##

The reaction of (31) with (32) is a Grignard synthesis which is knownper se, and the halogenation of (33) can be achieved with thionylchloride or a phosphorous halide.

The corresponding compounds (1) for Hal=F or I can be obtained bytrans-halogenation methods which are known per se, for example, inaccordance with the method of Finkelstein, from the products of thesynthesis according to equation III. The methods described byGerstenberger et al in Angew. Chemie 93 (1981) 659 are usually alsosuitable for introducing fluorine by trans-halogenation.

Suitable starting compounds of the formula (31) and (32) are againeither known or they can be obtained in a similar manner to the knowncompounds.

A further process for the preparation of compounds of the formula (1)comprises modifying the compounds (1) obtained in accordance withequation I or III, for example on the end groups R¹ and R², or bytreating the compounds in which X in the main bridge is halogen, such asbromine, with potassium cyanide.

It is furthermore possible to use, instead of the starting compounds ofthe formulae (11), (12), (31) and (32) given in equations I and III, thecorresponding precursors containing suitable reactive groups, forexample halogen atoms, hydroxyl groups, carboxyl groups or the like,instead of the end groups R¹ and R², and then to convert these into thedesired groups R¹ and R² by methods which are known per se when thesynthesis routes of I or III have ended.

The chemical reactions described above are generally disclosed in termsof their broadest application to the preparation of the compounds ofthis invention. Occasionally, the reactions may not be applicable asdescribed to each compound included within the disclosed scope. Thecompounds for which this occurs will be readily recognized by thoseskilled in the art. In all such cases, either the reactions can besuccessfully performed by conventional modifications known to thoseskilled in the art, e.g., by appropriate protection of interferinggroups, by changing to alternative conventional reagents, by routinemodification of reaction conditions, etc., or other reactions disclosedherein or otherwise conventional, will be applicable to the preparationof the corresponding compounds of this invention. In all preparationmethods, all starting materials are known or readily preparable fromknown starting materials.

Without further elaboration, it is believed that one skilled in the artcan, using the preceding description, utilize the present invention toits fullest extent. The following preferred specific embodiments are,therefore, to be construed as merely illustrative, and not limitative ofthe remainder of the disclosure in any way whatsoever. In the followingexamples, all temperatures are set forth uncorrected in degrees Celsius;unless otherwise indicated, all parts and percentages are by weight.

EXAMPLE 1 Preparation of1,2-bis-(4-trans-pentylcyclohexyl)-1-cyanoethane (formula (2), R⁴ =R⁵=-n-pentyl, X=CN, A=B=(1a))

0.5 g of metallic sodium was suspended in a solution of 1.93 g (0.01mole) of 4-trans-cyanomethyl-1-pentylcyclohexane in 10 ml of benzene.The suspension was heated at the reflux temperature for 60 minutes. 2.02g (0.01 mole) of 4-trans-bromomethyl-1-pentylcyclohexane were then addeddropwise, with stirring.

When the reaction had ended, the reaction mixture was poured onto dilutecold hydrochloric acid and the resulting mixture was extracted withdimethyl ether. The crude target product was purified by chromatographyover silica gel. Melting point 41.3° C., clear point 61.5° C. Δε=4.3.

The following compounds are prepared analogously:

1,2-bis-(4-trans-butylcyclohexyl)-1-cyanoethane

1,2-bis-(4-trans-propylcyclohexyl)-1-cyanoethane, melting point 43°,clear point 36°

1,2-bis-(4-trans-hexylcyclohexyl)-1-cyanoethane,

1,2-bis-(4-trans-heptylcyclohexyl)-1-cyanoethane,

1-(4-trans-pentylcyclohexyl)-2-(4-trans-propylcyclohexyl)-1-cyanoethane,melting point 45°, clear point 47°

1-(4-trans-pentylcyclohexyl)-2-(4-propylphenyl)-1-cyanoethane

1-(4-trans-pentylcyclohexyl)-2-(4-butylphenyl)cyanoethane

1-(4-trans-pentycyclohexyl)-2-(4-pentylphenyl)cyanoethane

1-(4-trans-pentylcyclohexyl)-2-(4-hexylphenyl)cyanoethane

1-(4-trans-pentylcyclohexyl)-2-(4-heptylphenyl)cyanoethane

1-(4-trans-pentylcyclohexyl)-2-(4-octylphenyl)cyanoethane

1-(4-trans-pentylcyclohexyl)-2-(4-butoxyphenyl)cyanoethane

1-(4-trans-pentylcyclohexyl)-2-(4-pentoxyphenyl)cyanoethane

1-(4-trans-pentylcyclohexyl)-2-(4-hexoxyphenyl)cyanoethane

1-(4-trans-pentylcyclohexyl)-2-(4-heptoxyphenyl)cyanoethane

1-(4-trans-pentylcyclohexyl)-2-(4-octoxyphenyl)cyanoethane

1-(4-trans-butylcyclohexyl)-2-(4-propylphenyl)cyanoethane

1-(4-trans-butylcyclohexyl)-2-(4-butylphenyl)cyanoethane

1-(4-trans-butylcyclohexyl)-2-(4-pentylphenyl)cyanoethane

1-(4-trans-butylcyclohexyl)-2-(4-hexylphenyl)cyanoethane

1-(4-trans-butylcyclohexyl)-2-(4-heptylphenyl)cyanoethane

1-(4-trans-butylcyclohexyl)-2-(4-octylphenyl)cyanoethane

1-(4-trans-butylcyclohexyl)-2-(4-butoxyphenyl)cyanoethane

1-(4-trans-butylcyclohexyl)-2-(4-pentoxyphenyl)cyanoethane

1-(4-trans-butylcyclohexyl)-2-(4-hexoxyphenyl)cyanoethane

1-(4-trans-butylcyclohexyl)-2-(4-heptoxyphenyl)cyanoethane

1-(4trans-butylcyclohexyl)-2-(4-octoxyphenyl)cyanoethane

1-(4-trans-propylcyclohexyl)-2-(4-propylphenyl)cyanoethane

1-(4-trans-propylcyclohexyl)-2-(4-butylphenyl)cyanoethane

1-(4-trans-propylcyclohexyl)-2-(4-pentylphenyl)cyanoethane

1-(4-trans-propylcyclohexyl)-2-(4-hexylphenyl)cyanoethane

1-(4-trans-propylcyclohexyl)-2-(4-heptylphenyl)cyanoethane

1-(4-trans-propylcyclohexyl)-2-(4-octylphenyl)cyanoethane

1-(4-trans-propylcyclohexyl)-2-(4-butoxyphenyl)cyanoethane

1-(4-trans-propylcyclohexyl)-2-(4-pentoxyphenyl)cyanoethane

1-(4-trans-propylcyclohexyl)-2-(4-hexoxyphenyl)cyanoethane

1-(4-trans-propylcyclohexyl)-2-(4-heptoxyphenyl)cyanoethane

1-(4-trans-propylcyclohexyl)-2-(4-octoxyphenyl)cyanoethane

1-(4-trans-pentylcyclohexyl)-2-[4-trans(p-propylphenyl)cyclohexyl]-cyanoethane

1-(4-trans-pentylcyclohexyl)-2-[4-trans(p-butylphenyl)cyclohexyl]-cyanoethane

1-(4-trans-pentylcyclohexyl)-2-[4-trans(p-pentylphenyl)cyclohexyl]-cyanoethane

1-(4-trans-pentylcyclohexyl)-2-[4-trans(p-hexylphenyl)cyclohexyl]-cyanoethane

1-(4-trans-pentylcyclohexyl)-2-[4-trans(p-heptylphenyl)cyclohexyl]-cyanoethane

1-(4-trans-pentylcyclohexyl)-2-[4-trans(p-octylphenyl)cyclohexyl]-cyanoethane

1-(4-trans-pentylcyclohexyl)-2-[4-trans(p-butoxyphenyl)cyclohexyl]-cyanoethane

1-(4-trans-pentylcyclohexyl)-2-[4-trans(p-pentoxyphenyl)cyclohexyl]-cyanoethane

1-(4-trans-pentylcyclohexyl)-2-[4-trans(p-hexoxyphenyl)cyclohexyl]-cyanoethane

1-(4-trans-pentylcyclohexyl)-2-[4-trans(p-heptoxyphenyl)cyclohexyl]-cyanoethane

1-(4-trans-pentylcyclohexyl)-2-[4-trans(p-octoxyphenyl)cyclohexyl]-cyanoethane

1-(4-trans-butylcyclohexyl)-2-[4-trans(p-propylphenyl)cyclohexyl]-cyanoethane

1-(4-trans-butylcyclohexyl)-2-[4-trans(p-butylphenyl)cyclohexyl]-cyanoethane

1-(4-trans-butylcyclohexyl)-2-[4-trans(p-phenylphenyl)cyclohexyl]-cyanoethane

1-(4-trans-butylcyclohexyl)-2-[4-trans(p-hexylphenyl)cyclohexyl]-cyanoethane

1-(4-trans-butylcyclohexyl)-2-[4-trans(p-heptylphenyl)cyclohexyl]-cyanoethane

1-(4-trans-butylcyclohexyl)-2-[4-trans(p-octylphenyl)cyclohexyl]-cyanoethane

1-(4-trans-butylcyclohexyl)-2-[4-trans(p-butoxyphenyl)cyclohexyl]-cyanoethane

1-(4-trans-butylcyclohexyl)-2-[4-trans(p-pentoxyphenyl)cyclohexyl]-cyanoethane

1-(4-trans-butylcyclohexyl)-2-[4-trans(p-hexoxyphenyl)cycloheyxl]-cyanoethane

1-(4trans-butylcyclohexyl)-2-[4-trans(p-heptoxyphenyl)cyclohexyl]-cyanoethane

1-(4-trans-butylcyclohexyl)-2-[4-trans(p-octoyphenyl)cyclohexyl]-cyanoethane

1-(4-trans-propylcyclohexyl)-2-[4-trans(p-propylphenyl)cyclohexyl]-cyanoethane

1-(4-trans-propylcyclohexyl)-2-[4-trans(p-butylphenyl)cyclohexyl]-cyanoethane

1-(4-trans-propylcyclohexyl)-2-[4-trans(p-pentylphenyl)cyclohexyl]-cyanoethane

1-(4-trans-propylcyclohexyl)-2-[4-trans(p-hexylphenyl)cyclohexyl]-cyanoethane

1-(4-trans-propylcyclohexyl)-2-[4-trans(p-heptylphenyl)cyclohexyl]-cyanoethane

1-(4-trans-propylcyclohexyl)-2-[4-trans(p-octylphenyl)cyclohexyl]-cyanoethane

1-(4-trans-propylcyclohexyl)-2-[4-trans(p-butoxyphenyl)cyclohexyl]-cyanoethane

(4-trans-propylcyclohexyl)-2-[4-trans(p-pentoxyphenyl)cyclohexyl]-cyanoethane

1-(4-trans-propylcyclohexyl)-2-[4-trans(p-heoxyphenyl)cyclohexyl]-cyanoethane

1-(4-trans-propylcyclohexyl)-2-[4-trans(p-heptoxyphenyl)cyclohexyl]-cyanoethane

1-(4-transpropylcyclohexyl)-2-[4-trans(p-octoxyheptoxyphenyl)cyclohexyl]-cyanoethane

1-(4-trans-pentylcyclohexyl)-2-(4'-propylbiphenyl)-1-cyanoethane

1-(4-trans-pentylcyclohexyl)-2-(4'-butylbiphenyl)-1-cyanoethane

1-(4-trans-pentylcyclohexyl)-2-(4'-pentylbiphenyl)-1-cyanoethane

1-(4-trans-pentylcyclohexyl)-2-(4'-hexylbiphenyl)-1-cyanoethane

1-(4-trans-pentylcyclohexyl)-2-(4'-heptylbiphenyl)-1-cyanoethane

1-(4-trans-pentylcyclohexyl)-2-(4'-octylbiphenyl)-1-cyanoethane

1-(4-trans-pentylcyclohexyl)-2-(4'-butopxybiphenyl)-1-cyanoethane

1-(4-trans-pentylcyclohexyl)-2-(4'-pentoxybiphenyl)-1-cyanoethane

1-(4-trans-pentylcyclohexyl)-2-(4'-hexoxybiphenyl)-1-cyanoethane

1-(4-trans-pentylcyclohexyl)-2-(4'-heptoxybiphenyl)-1-cyanoethane

1-(4-trans-pentylcyclohexyl)-2-(4'-octoxybiphenyl)-1-cyanoethane

1-(4-trans-propylcyclohexyl)-2-(4'-propylphenyl)-1-cyanoethane

1-(4-trans-propylcyclohexyl)-2-(4'-butylphenyl)-1-cyanoethane

1-(4-trans-propylcyclohexyl)-2-(4'-pentylphenyl)-1-cyanoethane

1-(4-trans-propylcyclohexyl)-2-(4'-hexylphenyl)-1-cyanoethane

1-(4-trans-propylcyclohexyl)-2-(4'-heptylphenyl)-1-cyanoethane

1-(4-trans-propylcyclohexyl)-2-(4'-octylphenyl)-1-cyanoethane

1-(4-trans-propylcyclohexyl)-2-(4'-butoxyphenyl)-1-cyanoethane

1-(4-trans-propylcyclohexyl)-2-(4'-pentoxyphenyl)-1-cyanoethane

1-(4-trans-propylcyclohexyl)-2-(4'-hexoxyphenyl)-1-cyanoethane

1-(4-trans-propylcyclohexyl)-2-(4'-heptoxyphenyl)-1-cyanoethane

1-(4-trans-propylcyclohexyl)-2-(4'-octoxyphenyl)-1-cyanoethane

1-(4-trans-heptylcyclohexyl)-2-(4'-propylphenyl)-1-cyanoethane

1-(4-trans-heptylcyclohexyl)-2-(4'-butylphenyl)-1-cyanoethane

1-(4-trans-heptylcyclohexyl)-2-(4'-pentylphenyl)-1-cyanoethane

1-(4-trans-heptylcyclohexyl)-2-(4'-hexylphenyl)-1-cyanoethane

1-(4-trans-heptylcyclohexyl)-2-(4'-heptylphenyl)-1-cyanoethane

1-(4-trans-heptylcyclohexyl)-2-(4'-octylphenyl)-1-cyanoethane

1-(4-trans-hepylcyclohexyl)-2-(4'-butoxyphenyl)-1-cyanoethane

1-(4-transl-heptylcyclohexyl)-2-(4'-pentoxyphenyl)-1-cyanoethane

1-(4-trans-heptylcyclohexyl)-2-(4'-hexoyphenyl)-1-cyanoethane

1-(4-trans-heptylcyclohexyl)-2-(4'-heptoxyphenyl)-1-cyanoethane

1-(4-trans-heptylcyclohexyl)-2-(4'-octoxyphenyl)-1-cyanoethane

EXAMPLE 2 Preparation of1-(4'-trans-pentyl-4-trans-bicyclohexyl)-2-(4-trans-pentylcyclohexyl)-2-cyanoethane(formula (5), R³ =R⁴ =n-pentyl).

0.5 g of sodium was added to 1.93 g (0.01 mole) of4-trans-cyanomethyl-1-pentylcyclohexane in 10 ml of benzene and themixture was heated at the reflux temperature for 60 minutes, withvigorous stirring.

0.01 Mole of4-trans-bromomethyl-1-(4-trans-pentylcyclohexyl)-cyclohexane was addedto the resulting dispersion, with stirring, and the mixture was heateduntil the reaction had ended. The reaction mixture was poured onto aHCl/ice mixture. The crude product was extracted from the resultingmixture with dimethyl ether and was chromatographed over silica gel forpurification. Melting point 71.5° C., clear point 173° C., Δε=-3.6,Δη=0.06.

The compound of the formula (V) ##STR19## which is not according to theinvention, was used for comparison with the target compound according tothe invention prepared in this example, because this comparison compoundhas approximately the same negative DCA as the compound of Example 2,although it requires two cyano groups on the ring to achieve this. Thiscomparison shows the surprising advantages of compounds (1) according tothe invention with a laterally polarizing group on the bridge as opposedto the prior art in two respects: on the one hand, according to theinvention, a DCA which is virtually just as negative can already beachieved with a single cyano group, but on the bridge, as is achievedwith two lateral cyano groups on the ring; this is probably to beattributed to the fact that the cyano group on the bridge causesvirtually no polarisation moment in the direction of the longitudinalaxis of the molecule, while the cyano groups on the ring causepolarization moments in this direction which are considerable but canceleach other out.

On the other hand, the compound according to the invention has a verybroad mesophase (71.5° to 173° C.), while the comparison compound has amelting point of 163° C. and has no mesophase at all.

The following compounds are prepared analogously:

1-(4'-trans-propyl-4-trans-bicyclohexyl)-2-(4-trans-propylcyclohexyl)-2-cyanoethane

1-(4'-trans-propyl-4-trans-bicyclohexyl)-2-(4-trans-butylcyclohexyl)-2-cyanoethane

1-(4'-trans-propyl-4-trans-bicyclohexyl)-2-(4-trans-pentylcyclohexyl)-2-cyanoethane

1-(4'-trans-propyl-4-trans-bicyclohexyl)-2-(4-trans-hexylcyclohexyl)-2-cyanoethane

1-(4'-trans-propyl-4-trans-bicyclohexyl)-2-(4-trans-heptylcyclohexyl)-2-cyanoethane

1-(4'-trans-butyl-4-trans-bicyclohexyl)-2-(4-trans-propylcyclohexyl)-2-cyanoethane

1-(4'-trans-butyl-4-trans-bicyclohexyl)-2-(4-trans-butylcyclohexyl)-2-cyanoethane

1-(4'-trans-butyl-4-trans-bicyclohexyl)-2-(4-trans-pentylcyclohexyl)-2-cyanoethane

1-(4'-trans-butyl-4-trans-bicyclohexyl)-2-(4-trans-hexylcyclohexyl)-2-cyanoethane

1-(4'-trans-butyl-4-trans-bicyclohexyl)-2-(4-trans-heptylcyclohexyl)-2-cyanoethane

1-(4'-trans-pentyl-4-trans-bicyclohexyl)-2-(4-trans-propylcyclohexyl)-2-cyanoethane,melting point 66°, clear point 165°

1-(4'-trans-pentyl-4-trans-bicyclohexyl)-2-(4-trans-butylcyclohexyl)-2-cyanoethane

1-(4'-trans-pentyl-4-trans-bicyclohexyl)-2-(4-trans-hexyl)cyclohexyl)-2-cyanoethane

1-(4'-trans-pentyl-4-trans-bicyclohexyl)-2-(4-trans-heptyl)cyclohexyl)-2-cyanoethane

1-(4'-trans-heptyl-4-trans-bicyclohexyl)-2-(4-trans-propylcyclohexyl)-2-cyanoethane

1-(4'-trans-heptyl-4-trans-bicyclohexyl)-2-(4-trans-butylcyclohexyl)-2-cyanoethane

1-(4'-trans-heptyl-4-trans-bicyclohexyl)-2-(4-trans-pentylcyclohexyl)-2-cyanoethane

1-(4'-trans-heptyl-4-trans-bicyclohexyl)-2-(4-trans-hexylcyclohexyl)-2-cyanoethane

1-(4'-trans-heptyl-4-trans-bicyclohexyl)-2-(4-trans-heptylcyclohexyl)-2-cyanoethane

1-(4'-trans-hexylcyclohexyl)-2-(4'-trans-propyl-4-trans-bicyclohexyl)-2-cyanoethane

1-(4'-trans-hexylcyclohexyl)-2-(4'-trans-butyl-4-trans-bicyclohexyl)-2-cyanoethane

1-(4'-trans-hexylcyclohexyl)-2-(4'-trans-pentyl-4-trans-bicyclohexyl)-2-cyanoethane

1-(4'-trans-hexylcyclohexyl)-2-(4'-trans-hexyl-4-trans-bicyclohexyl)-2-cyanoethane

1-(4'-trans-hexylcyclohexyl)-2-(4'-trans-heptyl-4-trans-bicyclohexyl)-2-cyanoethane

1-(4'-trans-propylcyclohexyl)-2-(4'-trans-propyl-4-trans-bicyclohexyl)-2-cyanoethane

1-(4'-trans-propylcyclohexyl)-2-(4'-trans-butyl-4-trans-bicyclohexyl)-2-cyanoethane

1-(4'-trans-propylcyclohexyl)-2-(4'-trans-bicyclohexyl)-2-cyanoethane,melting point 70°, clear point 167°

1-(4'-trans-propylcyclohexyl)-2-(4'-trans-hexyl-4-trans-bicyclohexyl)-2-cyanoethane

1-(4'-trans-propylcyclohexyl)-2-(4'-trans-heptyl-4-trans-bicyclohexyl)-2-cyanoethane

1-(4'-trans-pentylcyclohexyl)-2-(4'-trans-pentyl-4-trans-bicyclohexyl)-2-cyanoethane,melting point 60°, clear point 171°

1,2-(4∝-trans-pentyl-4-trans-bicyclohexyl)-2-cyanoethane, melting point123°, clear point 284°

1,2-bis-(4'-trans-butyl-4-trans-bicyclohexyl)-2-cyanoethane

1,2-bis-(4'-trans-propyl-4-trans-bicyclohecyl)-2-cyanoethane

EXAMPLE 3 Preparation of1,2-bis-(4-trans-propylcyclohexyl)-1-cyanoethane (formula (2), R⁴ =R⁵=n-propyl, X=Cn, A=B=(1a))

The target product was obtained by the process described in Example 1,by reacting 4-trans-cyanomethyl-1-propylcyclohexane with4-trans-bromomethyl-1-propylcyclohexane; melting point 45.7° C., clearpoint (37.0)°C.

Further examples of compounds according to the invention are mentionedbelow:

1,2-bis-(4-trans-propylcyclohexyl)-1-fluoro-ethane

1,2-bis-(4-trans-propylcyclohexyl)-1-chloro-ethane

1,2-bis-(4-trans-propylcyclohexyl)-1-bromo-ethane

1,2-bis-(4-trans-propylcyclohexyl)-1-cyano-ethane

1,2-bis-(4-trans-fluoropropylcyclohexyl)-1-cyano-ethane

1,2-bis-(4-trans-propyloxycarbonylcyclohexyl)-1-fluoro-ethane

1,2-bis-(4-trans-propyloxycarbonylcyclohexyl)-1-chloro-ethane

1,2-bis-(4-trans-propyloxycarbonylcyclohexyl)-1-bromo-ethane

1,2-bis-(4-trans-propyloxycarbonylcyclohexyl)-1-cyano-ethane

1,2-bis-(4-trans-fluoropropyloxycarbonylcyclohexyl)-1-cyano-ethane

1-(4'-trans-propyl-4-trans-bicyclohexyl)-2-(4trans-propylcyclohexyl)-2-fluoro-ethane

1-(4'-trans-propyl-4-trans-bicyclohexyl)-2-(4-trans-propylcyclohexyl)-2-chloro-ethane

1-(4'-trans-propyl-4-trans-bicyclohexyl)-2-(4-trans-propylcyclohexyl)-2-bromo-ethane

1-(4'-trans-propyl-4-trans-bicyclohexyl)-2-(4-trans-propyloxycarbonylcyclohexyl)-2-fluoro-ethane

1-(4'-trans-propyl-4-trans-bicyclohexyl)-2-(4-trans-propyloxycarbonylcyclohexyl)-2-chloro-ethane

1-(4'-trans-propyl-4-trans-bicyclohexyl)-2-(4-trans-propyloxycarbonylcyclohexyl)-2-bromo-ethane

1-(4'-trans-propyl-4-trans-bicyclohexyl)-2-(4-trans-propyloxycarbonylcyclohexyl)-2-cyano-ethane

1-(4-trans(2-(4-trans-propylcyclohexyl)-ethyl)-cyclohexyl)-2-(4-trans-propylcyclohexyl)-2-fluoro-ethane

1-(4-trans-(2-(4-trans-propylcyclohexyl)-ethyl)-cyclohexyl)-2-(4-trans-propylcyclohexyl)-2-chloro-ethane

1-(4-trans-(2-(4-trans-propylcyclohexyl)-ethyl)-cyclohexyl)-2-(4-trans-propylcyclohexyl)-2-bromo-ethane

1-(4-trans-(2-(4-trans-propylcyclohexyl)-ethyl)-cyclohexyl)-2-(4-trans-propylcyclohexyl)-2-cyano-ethane

1-(4-trans-(2-(4-trans-propylcyclohexyl)-1-fluoroethyl)cyclohexyl)-2-(4-trans-propylcyclohexyl)-2-fluoro-ethane

1-(4-trans-(2-(4-trans-propylcyclohexyl)-1-fluoroethyl)cyclohexyl)-2-(4-trans-propylcyclohexyl)-2-cyano-ethane

1-(4-trans-(2-(4-trans-propylcyclohexyl)-1-cyanoethyl)cyclohexyl)-2-(4-trans-propylcyclohexyl)-2-fluoro-ethane

1-(4-trans-(2-(4-trans-propylcyclohexyl)-1-cyanoethyl)cyclohexyl)-2-(4-trans-propylcyclohexyl)-2-cyano-ethane

1-(4-propyl-1-bicyclo-(2,2,2)-octyl)-2-(4-trans-propylcyclohexyl)-1-fluoro-ethane

1-(4-1-bicyclo-(2,2,2)-octyl)-2-(4-trans-propylcyclohexyl)-1-chloro-ethane

1-(4-propyl-1-bicyclo-(2,2,2)-octyl)-2-(4-trans-propylcyclohexyl)-1-bromo-ethane

1-(4-propyl-1-bicyclo-(2,2,2)-octyl)-2-(4-trans-propylcyclohexyl)-1-cyano-ethane

1-(4-propyl-1-bicyclo-(2,2,2)-octyl)-2-(4-trans-propyloxycarbonylcyclohexyl)-1-fluoro-ethane

1-(4-propyl--bicyclo-(2,2,2)-octyl)-2-(4-trans-propyloxycarbonylcyclohxyl)-1-cyano-ethane

1-(4-trans-propylcyclohexyl)-2-(4-pentylphenyl)-1-fluoro-ethane

1-(4-trans-propylcyclohexyl)-2-(4-pentylphenyl)-1-chloro-ethane

1-(4-trans-propylcyclohexyl)-2-(4-pentylphenyl)-1-bromo-ethane

1-(4-trans-propylcyclohexyl)-2-(4-pentylphenyl)-1-cyano-ethane

1-(4-trans-propylcyclohexyl)-2-(4-butoxyphenyl)-1-fluoro-ethane

1-(4-trans-propylcyclohexyl)-2-(4-butoxyphenyl)-1-chloro-ethane

1-(4-trans-propylcyclohexyl)-2-(4-butoxyphenyl)-1-bromo-ethane

1-(4-trans-propylcyclohexyl)-2-(4-butoxyphenyl)-1-cyano-ethane

1-(4-trans-propylcyclohexyl)-2-(4-(4-trans-pentylcyclohexyl)-phenyl)-1-fluoro-ethane

1-(4-trans-propylcyclohexyl)-2-(4-(4-trans-pentylcyclohexyl)-phenyl)-1-chloro-ethane

1-(4-trans-propylcyclohexyl)-2-(4-(4-trans-pentylcyclohexyl)-phenyl-1-bromo-ethane

1-(4-trans-propylcyclohexyl)-2-(4-(4-tans-pentylcyclohexyl)-phenyl)-1-cyano-ethane

1-(4-trans-propylcyclohexyl)-2-(4-(4-trans-pentylcyclohex-1-yl-methoxy)-phenyl)-1-fluoro-ethane

1-(4-trans-propylcyclohexyl)-2-(4-(4-trans-pentylcyclohex-1-yl-methoxy)-phenyl)-1-chloro-ethane

1-(4-trans-propylcyclohexyl)-2-(4-(4-trans-pentylcyclohex-1-yl-methoxy)-phenyl)-1-bromo-ethane

1-(4-trans-propylcyclohexyl)-2-(4-(4-trans-pentylcyclohex-1-yl-methoxy)-phenyl)-1-cyano-ethane

1-(4-trans-propylcyclohexyl)-2-(4-trans-(4-pentylphenyl)-cyclohexyl)-1-fluoro-ethane

1-(4-trans-propylcyclohexyl)o-2-(4-trans-(4-pentylphenyl)-cyclohexyl)-1-chloro-ethane

1-(4-trans-propylcyclohexyl)-2-(4-trans-(4-pentrylphenyl)-cyclohexyl)-1-bromo-ethane

1-(4-trans-propylcyclohexyl)-2-(4-trans-(4-pentylphenyl)-cyclohexyl)-1-cyano-ethane

1-(4-trans-propylcyclohexyl)-2-(4-trans-(4-butoxyphenyl)-cyclohexyl)-1-fluoro-ethane

1-(4-trans-propylcyclohexyl)-2-(4-trans-(4-butoxyphenyl-cyclohexyl)-1-chloro-ethane

1-(4-trans-propylcyclohexyl)-2-(4-trans-(4-butoxyphenyl)-cyclophexyl)-1-bromo-ethane

1-(4-trans-propylcyclohexyl)-2-(4-trans-(4-butoxyphenyl)-cyclohexyl)-1-cyano-ethane

1-(4-trans-propylcyclohexyl)-2-(4-trans-(4-pentylphenoxymethyl)-cyclohexyl)-1-fluoro-ethane

1-(4-trans-propylcyclohexyl)-2-(4-trans-(4-pentylphenoxymethyl)-cyclohexyl)-1-chloro-ethane

1-(4-trans-propylcyclohexyl)-2-(4-trans-(4-pentylphenoxymethyl)cyclohexyl)-1-bromo-ethane

1-(4-trans-propylcyclohexyl)-2-(4-trans-(4-pentylphenoxymethyl)-cyclohexyl)-1-cyano-ethane

1-(4-trans-propylcyclohexyl)-2-(4-trans-(4-butoxyphenoxymethyl)-cyclohexyl)-1-fluoro-ethane

1-(4-trans-propylcyclohexyl)-2-(4-trans-(4-butoxyphenoxymethyl)-cyclohexyl)-1-chloro-ethane

1-(4-trans-propylcyclohexyl)-2-(4-trans-(4-butoxyphenoxymethyl)-cyclohexyl)-1-bromo-ethane

1-(4-trans-propylcyclohexyl)-2-(4-trans-(4-butoxyphenoxymethyl)-cyclohexyl)-1-cyano-ethane

1-(4-propyl-1-bicyclo-(2,2,2)-octyl)-2-(4-trans-(4-pentylphenyl)-cyclohexyl)-1-fluoro-ethane

1-(4-propyl-1-bicyclo-(2,2,2)-octyl)-2-(4-trans-(4-pentylphenyl)-cyclohexyl)-1-chloro-ethane

1-(4-propyl-1-bicyclo-(2,2,2)-octyl)-2-(4-trans-(4-pentylphenyl)-cyclohexyl)-1-bromo-ethane

1-(4-propyl-1-bicyclo-(2,2,2)-octyl)-2-(4-trans-(4-pentylphenyl)-cyclohexyl)-1-cyano-ethane

1-(4-propyl-1-bicyclo-(2,2,2)-octyl)-2-(4-trans-(4-butoxyphenyl)-cyclohexyl)-1-fluoro-ethane

1-(4-propyl-1-bicyclo-(2,2,2)-octyl)-2-(4-trans-(4-butoxyphenyl)-cyclohexyl)-1-chloro-ethane

1-(4-propyl-1-bicyclo-(2,2,2)-octyl)-2-(4-trans-(4-butoxyphenyl)-cyclohexyl)-1-bromo-ethane

1-(4-propyl-1-bicyclo-(2,2,2)-octyl)-2-(4-trans-(4-butoxyphenyl)-cyclohexyl)-1-cyano-ethane

1-(4-propyl-1-bicyclo-(2,2,2)-octyl)-2-(4-(4-trans-pentylcyclohexyl)-phenyl-1-fluoro-ethane

1-(4-propyl-1-bicyclo-(2,2,2)-octyl)-2-(4-(4-trans-pentylcyclohexyl)-phenyl-1-chloro-ethane

1-(4-propyl-1-bicyclo-(2,2,2)-octyl)-2-(4-trans-pentylcyclohexyl)-phenyl-1-bromo-ethane

1-(4-propyl-1-bicyclo-(2,2,2)-octyl)-2-(4-(4-trans-pentylcyclohexyl)-phenyl-1-cyano-ethane

1-(4-propyl-1-bicyclo-(2,2,2)-octyl)-2-(4-(4-trans-propyloxycarbonylcyclohexyl)-phenyl)-1-fluoro-ethane

1-(4-propyl-1-bicyclo-(2,2,2)-octyl)-2-(4-(4-trans-propyloxycarbonylcyclohexyl)-phenyl)-1-chloro-ethane

1-(4-propyl-1-bicyclo-(2,2,2)-octyl)-2-(4-(4-trans-propyloxycarbonylcyclohexyl)-phenyl)-1-bromo-ethane

1-(4-propyl-1-bicyclo-(2,2,2)-octyl)-2-(4-(4-trans-propyloxycarbonylcyclohexyl)-phenyl)-1-cyano-ethane

1-(4-trans-propyl-cyclohexyl)-2-(6-pentylpyridazin-3-yl)-1-fluoro-ethane

1-(4-trans-propyl-cyclohexyl)-2-(6-pentylpyridazin-3-yl)-1-chloro-ethane

1-(4-trans-propyl-cyclohexyl)-2-(6-pentylpyridazin-3-yl)-1-bromo-ethane

1-(4-trans-propyl-cyclohexyl)-2-(6-pentylpyridazin-3-yl)-1-cyano-ethane

1-(4-trans-propylcyclohexyl)-2-(6-butoxypyridazin-3-yl)-1-fluoro-ethane

1-(4-trans-propylcyclohexyl)-2-(6-butoxypyridazin-3-yl)-1-chloro-ethane

1-(4-trans-propylcyclohexyl)-2-(6-butoxypyridazin-3-yl)-1-bromo-ethane

1-(4-trans-propylcyclohexyl)-2-(6-butoxypyridazin-3-yl)-1-cyano-ethane

1-(4-trans-propylcyclohexyl)-2-(4-trans-(6-pentylpyridazin-3-yl)-cyclohexyl)-1-fluoro-ethane

1-(4-trans-propylcyclohexyl)-2-(4-trans-(6-pentylpyridazin-3-yl)-cyclohexyl)-1-chloro-ethane

1-(4-trans-propylcyclohexyl)-2-(4-trans-(6-pentylpyridazin-3-yl)-cyclohexyl)-1-bromo-ethane

1-(4-trans-propylcyclohexyl)-2-(4-trans-(6-pentylpyridazin-3-yl)-cyclohexyl)-1-cyano-ethane

1-(4-trans-propylcyclohexyl)-2-(4-trans-(6-butoxypyridazin-3-yl)-cyclohexyl)-1-fluoro-ethane

1-(4-trans-propylcyclohexyl)-2-(4-trans-(6-butoxypyridazin-3-yl)-cyclohexyl-1-chloro-ethane

1-(4-trans-propylcyclohexyl)-2-(4-trans-(6-butoxypyridazin-3-yl)-cyclohexyl-1-bromo-ethane

1-(4-trans-propylcyclohexyl)-2-(4-trans-(6-butoxypyridazin-3-yl)-cyclohexyl)-1-cyano-ethane

1-(4-trans-propylcyclohexyl)-2-(4-trans-(2-(6-pentylpyridazin-3-yl-ethyl)-cyclohexyl)-1-fluoro-ethane

1-(4-trans-propylcyclohexyl)-2-(4-trans-(2-(6-pentylpyridazin-3-yl)-ethyl)-cyclohexyl)-1-chloro-ethane

1-(4-trans-propylcyclohexyl)-2-(4-trans-(2-(6-pentylpyridazin-3-yl)-ethyl)-cyclohexyl)-1-bromo-ethane

1-(4-trans-propylcyclohexyl)-2-(4-trans-(2-(6-pentylpyridazin-3-yl)-ethyl)-cyclohexyl)-1-cyano-ethane

1-(4-trans-propylcyclohexyl)-2-(4-trans-(2-(6-butoxypyridazin-3-yl)-ethyl)-cyclohexyl)-1-fluoro-ethane

1-(4-trans-propylcyclohexyl)-2-(4-trans-(2-(6-butoxypyridazin-3-yl)-ethyl)-cyclohexyl)-1-bromo-ethane

1-(4-trans-propylcyclohexyl)-2-(4-trans-(2-(6-butoxypyridazin-3-yl)-ethyl)-cyclohexyl)-1-chloro-ethane

1-(4-trans-propylcyclohexyl)-2-(4-trans-(2-(6-butoxypyridazin-3-yl)-ethyl)-cyclohexyl)-1-cyano-ethane

1-(4-trans-propylcyclohexyl)-2-(6-(4-trans-pentylcyclohexyl)-pyridazin-3-yl)-1-fluoro-ethane

1-(4-trans-propylcyclohexyl)-2-(6-(4-trans-pentylcyclohexyl)-pyridazin-3-yl)-1-chloro-ethane

1-(4-trans-propylcyclohexyl)-2-(6-(4-trans-pentylcyclohexyl)-pyridazin-3-yl)-1-bromo-ethane

1-(4-trans-propylcyclohexyl)-2-(6-(4-trans-pentylcyclohexyl)-pyridazin-3-yl)-1-cyano-ethane

1-(4-trans-propylcyclohexyl)-2-(6-(2-(4-trans-pentylcyclohexyl)-ethyl)-pyridazin-3-yl)-1-fluoro-ethane

1-(4-trans-propylcyclohexyl)-2-(6-(2-(4-trans-pentylcyclohexyl)-ethyl)-pyridazin-3-yl)-1-chloro-ethane

1-(4-trans-propylcyclohexyl)-2-(6-(2-(4-trans-pentylcyclohexyl)-ethyl)-pyridazin-3-yl)-1-bromo-ethane

1-(4-trans-propylcyclohexyl)-2-(6-(2-(4-trans-pentylcyclohexyl)-ethyl)-pyridazin-3-yl)-cyano-ethane

1,2-bis-(4-trans-cyanomethylcyclohexyl)-1-fluoro-ethane

1,2-bis-(4-trans-cyanopropylcyclohexyl)-1-fluoro-ethane

1-(4'-trans-fluoropropyl-4-trans-bicyclohexyl)-2-(4-trans-fluoropropylcyclohexyl)-2-chloro-ethane

1-(4'-trans-fluoropropyl-4-trans-bicyclohexyl)-2-(4-trans-fluoropropylcyclohexyl)-2-cyano-ethane

1-(4'-trans-fluoropropyl-4-trans-bicyclohexyl)-2-(4-trans-fluoropropyloxycarbonylcyclohexyl)-2-chloroethane

1-(4'-trans-fluoropropyl-4-trans-bicyclohexyl)-2-(4-trans-fluoropropyloxycarbonylcyclohexyl)-2-cyano-ethane

1-(4-trans-(2-(4-trans-cyanopropylcyclohexyl)-ethyl)-cyclohexyl)-2-(4-trans-propylcyclohexyl)-2-fluoro-ethane

1-(4-trans-(2-(4-trans-fluoropropylcyclohexyl)-ethyl)-cyclohexyl)-2-(4-trans-propylcyclohexyl)-2-fluoro-ethane

1-(4-trans-(2-(4-trans-chloropropylcyclohexyl)-ethyl)-cyclohexyl)-2-(4-trans-propylcyclohexyl)-2-chloro-ethane

1-(4-trans-(2-(4-trans-cyanopropylcyclohexyl)-ethyl)-cyclohexyl)-2-(4-trans-propylcyclohexyl)-2-cyano-ethane

1-(4-trans-cyanopropylcyclohexyl)-2-(4-pentylphenyl)-1-fluoro-ethane

1-(4-trans-fluoropropylcyclohexyl)-2-(4-pentylphenyl)-1-fluoro-ethane

1-(4-trans-chloropropylcyclohexyl)-2-(4-pentylphenyl)-1-chloro-ethane

1-(4-trans-cyanopropylcyclohexyl)-2-(4-pentylphenyl)-1-cyano-ethane

1-(4-trans-cyanopropylcyclohexyl)-2-(4-butoxyphenyl)-1-fluoro-ethane

1-(4-trans-fluoropropylcyclohexyl)-2-(4-butoxyphenyl)-1-fluoro-ethane.

1,2-bis-(4-trans-heptylcyclohexyl)-1-cyanoethane

1,2-bis-(4-trans-hexylcyclohexyl)-1-cyanoethane

1,2-bis-(4-trans-butylcyclohexyl)-1-cyanoethane

1,2-bis-(4-trans-propylcyclohexyl)-1-cyanoethane

1-(4-trans-propylcyclohexyl)-2-(4-trans-butylcyclohexyl)-1-cyanoethane

1-(4-trans-propylcyclohexyl)-2-(4-trans-pentylcyclohexyl)-1-cyanoethane

1-(4-trans-propylcyclohexyl)-2-(4-trans-hexylcyclohexyl)-1-cyanoethane

1-(4-trans-propylcyclohexyl)-2-(4-trans-heptylcyclohexyl)-1-cyanoethane

1-(4-trans-butylcyclohexyl)-2-(4-trans-pentylcyclohexyl)-1-cyanoethane

1-(4-trans-butylcyclohexyl)-2-(4-trans-hexylcyclohexyl)-1-cyanoethane

1-(4-trans-butylcyclohexyl)-2-(4-trans-heptylcyclohexyl)-1-cyanoethane

1-(4-trans-pentylcyclohexyl)-2-(4-trans-hexylcyclohexyl)-1-cyanoethane

1-(4-trans-pentylcyclohexyl)-2-(4-trans-heptylcyclohexyl)-1-cyanoethane

1-(4-trans-hexylcyclohexyl)-2-(4-trans-heptylcyclohexyl)-1-cyanoethane

The following examples relate to liquid crystal mixtures according tothe invention comprising at least one component of the formula (1):

EXAMPLE A

A liquid crystal mixture consisting of

    ______________________________________                                        11% by weight                                                                            trans,trans-4-propyl-4' -methoxycyclo-                                        hexylcyclohexane,                                                  10% by weight                                                                            trans,trans-4-propyl-4' -ethoxycyclohexyl-                                    cyclohexane,                                                        4% by weight                                                                            trans,trans-4-propylcyclohexylcyclohexane-                                    4'-carboxylic acid-trans-4-propylcyclo-                                       hexylester,                                                         4% by weight                                                                            trans,trans-4-propylcyclohexylcyclohexane-                                    4'-carboxylic acid-trans-4-pentylcyclo-                                       hexylester,                                                         4% by weight                                                                            trans,trans-4-butylcyclohexylcyclohexane-                                     4'-carboxylic acid-trans-4-propylcyclo-                                       hexylester,                                                         4% by weight                                                                            trans-trans-4-butylcyclohexylcyclohexane-                                     4'-carboxylic acid-trans-4-pentylcyclo-                                       hexylester,                                                        34% by weight                                                                            1-(4-trans-buty cyclohexy)-2-(4-trans-                                        heptylcyclohexyl)-1-cyanoethane and                                29% by weight                                                                            1,2-bis-(4-trans-pentylcyclohexyl)-1-                                         cyanoethane                                                        ______________________________________                                    

has a negative DCA.

EXAMPLE B

A liquid crystal mixture consisting of

    ______________________________________                                        20% by weight                                                                            1,2-bis-(4-trans-propylcyclohexyl)-1-                                         cyanoethane                                                        21% by weight                                                                            1,2-bis-(4-trans-pentylcyclohexyl)-1-                                         cyanoethane                                                        22% by weight                                                                            1-(4'-trans-pentyl-4-trans-bicyclohexy)-                                      2-(4-trans-pentylcyclohexyl)-2-cyanoethane,                        11% by weight                                                                            trans,trans-4-propyl-4'-methoxycyclohexyl-                                    cyclohexane                                                        10% by weight                                                                            trans,trans-4-propyl-4'-ethoxycyclohexyl-                                     cyclohexane                                                         4% by weight                                                                            trans,trans-4-propylcyclohexylcyclohexane-                                    4'-carboxylic acid-trans-4-propylcyclo-                                       hexylester,                                                         4% by weight                                                                            trans-trans-4-propylcyclohexylcyclohexane-                                    4'-carboxylic acid-trans-4-pentylcyclo-                                       hexylester,                                                         4% by weight                                                                            trans,trans-4-butylcyclohexylcyclohexane-                                     4'-carboxylic acid-trans-4-propylcyclo-                                       hexylester ,                                                        4% by weight                                                                            trans,trans-4-butylcyclohexylcylohexane-                                      4'-carboxylic acid-trans-4-pentylcyclo-                                       hexylester,                                                        ______________________________________                                    

has a negative DCA.

EXAMPLE C

A liquid crystal mixture consisting of

    ______________________________________                                        30% by weight                                                                            1-(4-trans-butylcyclohexyl)-2-(4-trans-                                       heptylcyclohexyl)-1-cyanoethane,                                   16% by weight                                                                            trans,trans-4-propyl-4'-methoxycyco-                                          hexylcyclohexane                                                   15% by weight                                                                            trans,trans-4-propyl-4'-ethoxycyclo-                                          hexylcyclohexane,                                                   4% by weight                                                                            trans,trans-4-propylcyclohexylcyclohexane-                                    4'-carboxylic acid-trans-4-propylcyclo-                                       hexylester,                                                         4% by weight                                                                            trans,trans-4-propylcyclohexylcyclohexane-                                    4'-carboxylic acid-trans-4-pentylcyclo-                                       hexylester,                                                         4% by weight                                                                            trans,trans-4-butylcyclohexylcyclohexane-                                     4'-carboxylic acid-trans-4-propylcyco-                                        hexylester                                                          4% by weight                                                                            trans,trans-4-butylcyclohexylcyclohexane-                                     4'-carboxylic acid-trans-4-pentylcyclo-                                       hexylester                                                          8% by weight                                                                            trans-4-propylcyclohexane-carboxylic                                          acid-(trans-4-propylcyclohexylester),                               7% by weight                                                                            trans-4-pentylcyclohexane-carboxylic                                          acid-(trans-4-pentycyclohexylester) and                             8% by weight                                                                            trans-4-hexylcyclohexane carboxylic                                           acid-(trans-4-heptylcyclohexylester)                               ______________________________________                                    

has a negative DCA.

The preceding examples can be repeated with similar success bysubstituting the generically or specifically described reactants and/oroperating conditions of this invention for those used in the precedingexamples. From the foregoing description, one skilled in the art caneasily ascertain the essential characteristics of this invention, andwithout departing from the spirit and scope thereof, can make variouschanges and modifications of the invention to adapt it to various usagesand conditions.

What is claimed is:
 1. A compound of the formula ##STR20## wherein x iscyano or halo, A is a cycloaliphatic radical of the formula (1a) or (1b)##STR21## B is a cycloaliphatic radical of the formula (1a) or (1b) oran aromatic radical of the formula (1c) or (1d) ##STR22## R¹ and R² areidentical or different and each is a radical of the formula (1e)##STR23## C has one of the meanings given for ring B, R³ is hydrogen,alkyl, alkoxy, alkoxy-carbonyl or alkylcarbonyloxy wherein the alkylportion of each contains 1-12 C atoms, or such a C₁₋₁₂ -group whichcarries one or more substituents which are halo or cyano, at most one ofthese substituents being attached to each atom of the carbon chain,Z isa covalent bond or a bridge group of the formula --CH₂ O--, --OCH₂ --,--C(X¹)(H)--CH₂ --, --CH₂ --C(X¹)(H)--, --OOC-- or --COO--, X¹ ishydrogen or has one of the meanings given for X, and m is 0 or 1, withthe provisos that(a) groups of the formula --CH₂ O-- or --C(X)(H)-- arenot bonded directly via their C atoms to any aromatic radical of theformula (1c) or (1d) present in the molecule, except when X=F, and (b)R³ is not hydrogen if m is 0 or if C is cycloaliphatic.
 2. A compound ofclaim 1, wherein in formula (1), X is cyano.
 3. A compound of claim 1,wherein formula (1) contains a total of two, three or fourcycloaliphatic radicals of the formula (1a).
 4. A compound of claim 1,wherein the alkyl portion of R³ contains 3-9 C atoms.
 5. A compound ofclaim 1 having formula (2) ##STR24## wherein X, A and B are as definedin claim 1 and R⁴ and R⁵ are identical or different and have one of themeanings given for R³, with the exception of hydrogen.
 6. A compound ofclaim 1, having the formula (3) ##STR25## wherein X, A, B, C, Z and R³are as defined in claim 1 and R⁴ has one of the meanings given for R³.7. A compound of claim 1, having the formula (4) ##STR26## wherein X, A,B, C, Z and R³ are as defined in claim 1 and R⁴ has one of the meaningsgiven for R³.
 8. A compound of claim 5, wherein X is cyano.
 9. Acompound of claim 6, wherein X is cyano.
 10. A compound of claim 7,wherein X is cyano.
 11. A compound of claim 1, having the formula (5)##STR27## wherein R⁴ has one of the meanings given for R³ in claim 1,and R³ and R⁴ are identical or different but are not hydrogen.
 12. Acompound of claim 11, wherein R³ and R⁴ are each a C₁ -C₁₂ -alkylradical.
 13. A compound of claim 12, wherein at least one of R³ and R⁴is n-pentyl.
 14. A compound of claim 1, wherein the alkyl portions arestraight chained.
 15. A compound of claim 1, having the formula (6)##STR28## wherein R¹ and R² are as defined in claim
 1. 16. A compound ofclaim 15, wherein R¹ is a C₁₋ C₁₂ --alkyl radical and R² is R³ ##STR29##17. A compound of claim 1, having the formula (7) ##STR30## wherein R¹and R³ are as defined in claim 1 and n is 0 or 1.